Стратегія на Python

from __future__ import annotations from abc import ABC, abstractmethod from typing import List class Context(): """ The Context defines the interface of interest to clients. """ def __init__(self, strategy: Strategy) -> None: """ Usually, the Context accepts a strategy through the constructor, but also provides a setter to change it at runtime. """ self._strategy = strategy @property def strategy(self) -> Strategy: """ The Context maintains a reference to one of the Strategy objects. The Context does not know the concrete class of a strategy. It should work with all strategies via the Strategy interface. """ return self._strategy @strategy.setter def strategy(self, strategy: Strategy) -> None: """ Usually, the Context allows replacing a Strategy object at runtime. """ self._strategy = strategy def do_some_business_logic(self) -> None: """ The Context delegates some work to the Strategy object instead of implementing multiple versions of the algorithm on its own. """ # ... print("Context: Sorting data using the strategy (not sure how it'll do it)") result = self._strategy.do_algorithm(["a", "b", "c", "d", "e"]) print(",".join(result)) # ... class Strategy(ABC): """ The Strategy interface declares operations common to all supported versions of some algorithm. The Context uses this interface to call the algorithm defined by Concrete Strategies. """ @abstractmethod def do_algorithm(self, data: List): pass """ Concrete Strategies implement the algorithm while following the base Strategy interface. The interface makes them interchangeable in the Context. """ class ConcreteStrategyA(Strategy): def do_algorithm(self, data: List) -> List: return sorted(data) class ConcreteStrategyB(Strategy): def do_algorithm(self, data: List) -> List: return reversed(sorted(data)) if __name__ == "__main__": # The client code picks a concrete strategy and passes it to the context. # The client should be aware of the differences between strategies in order # to make the right choice. context = Context(ConcreteStrategyA()) print("Client: Strategy is set to normal sorting.") context.do_some_business_logic() print() print("Client: Strategy is set to reverse sorting.") context.strategy = ConcreteStrategyB() context.do_some_business_logic() 

Client: Strategy is set to normal sorting. Context: Sorting data using the strategy (not sure how it'll do it) a,b,c,d,e Client: Strategy is set to reverse sorting. Context: Sorting data using the strategy (not sure how it'll do it) e,d,c,b,a